The present invention concerns an adhesive cartridge which is adapted to receive adhesive which is liquid or which is to be liquefied under the influence of heat and is usually used together with a hot-melt applicator device which provides for a suitable supply of heat.
Hot-melt adhesive applicator devices of that kind, as are described for example in the applicants"" German patent application No 100 10 304.9 make it possible, in a flexible procedure which is advantageous in terms of handling, to heat an adhesive which is suitably selected according to the respective area of use involved, in an associated cartridge, to the operating temperature, and then apply it by means of a unit in the form of a gun, so that it is possible to make use of the advantages of a hot-melt adhesive under a large number of conditions of use.
A particular advantage of such applicator devices is moreover that the modularity of the entire device, which is achieved by virtue of using cartridges, not only makes it possible to interchange various adhesive cartridges (which ideally are suitably identified), but rapid and efficient re-filling is also possible in a continuous operating procedure.
In practice however it has been found that there is the disadvantage that a (typically cylindrical) adhesive cartridge for hot-melt adhesive could not be fixed in its position within the heating element of an applicator device, so that problems arose in particular in regard to the transfer of heat from the heating element to the cartridge body and consequently then when heating the hot-melt adhesive contained in the cartridge body. At the same time, in consideration of a heating element which typically is embodied in the form of an aluminum extrusion of cylindrical internal cross-section, the provision of any elements which fix a relative position of the cartridge and the heating element with respect to each other was ruled out. Other conventional constructions such as for example screwing in the cartridge in contrast appear to be time-consuming and, particularly in consideration of the risk of contamination due to adhesive which has escaped, impracticable from the point of view of practical operation.
A further problem with cartridges of the general kind specified, which arises out of the principle involved, is that accurate metering of the medium in the cartridge, in particular the adhesive, can be achieved only with difficulty: as a filled cartridge (filled with liquid adhesive or adhesive to be liquefied) is to be considered as a closed or self-contained system, in which case the medium is discharged from the spout portion by actuation of the piston element from the opposite end of the cartridge body (with an increase in pressure that this entails, by virtue of compression of the medium in the cartridge), pressure equalisation is effected only by way of the discharge end or the spout portion. Emptying of the cartridge takes place until pressure equalisation has occurred between atmospheric pressure and the pressure within the cartridge, and this has the effect that the medium (adhesive) then still also issues from the cartridge although the piston is no longer being moved.
Particularly in the present context of use, namely applying liquid adhesive issuing from the spout portion, such a situation is unsatisfactory for, as will be appreciated, it is precisely a hot-melt adhesive which is used by virtue of its advantageous adhesive properties that must be accurately metered, and contamination caused by adhesive which unintentionally issues gives rise to unnecessary cleaning expenditure and complication and gives rise to specific practical problems in the area surrounding the position of application.
The object of the present invention is to facilitate the handleability of adhesive cartridges within an associated applicator device and in particular to improve the transmission of heat from a heating element to the adhesive cartridge. Another object of the present invention is to improve the handleability of adhesive cartridges of the general kind set forth, in regard to precisely meterable discharge of adhesive from the discharge end by actuation of the piston end, in particular insofar as discharge (outflow) of adhesive from the discharge end is to be prevented as soon as the piston element is not subjected to any pressure acting thereon (that is to say in particular unintentional discharge flow of adhesive is to be prevented).
The foregoing objects are attained by a device having an adhesive cartridge for accommodating liquid adhesive or adhesive which is to be liquefied and for insertion into a hot-melt adhesive applicator device, comprising a cylindrical cartridge body which is adapted for heating by a heating element of the hot-melt adhesive applicator device, which heating element acts on the cartridge at the periphery thereof in an at least region-wise manner, which cartridge body is adapted at one end for closure with an insertable piston element and at the other end has a spout portion providing an internal cross-section which is reduced with respect to the cylindrical cartridge body and which has an outlet end, wherein the adhesive cartridge has means for preventing rotation of the adhesive cartridge in an inserted condition relative to the hot-melt adhesive applicator device and/or relative to the heating element.
In a manner which is advantageous in accordance with the invention the rotation-preventing means provided on the adhesive cartridge in accordance with a first embodiment of the invention provide for a clearly defined, firm fit for the cartridge in the heating element so that play can be reduced and heat transfer can be improved. As a consequence, the handling properties are thereby markedly improved in practical use, and not least also, for example in an operative condition of the applicator device in which it is separated from a basic power supply, the adhesive contained in the cartridge remains fluid for use over a longer period of time.
In that respect it has proven to be particularly preferable in practical use for the rotation-preventing means to be provided in the region of the spout portion of the adhesive cartridge, that is to say, it is preferable for the rotation-preventing means to be so designed that it is (only) in a fully inserted condition of the cartridge into the heating element that the rotation-preventing means is in an engaging condition and provides for the advantageous fixing effect. Associated receiving means for the rotation-preventing means which in a further preferred feature are in the form of projections can then be provided in the applicator device outside the heating element and are thus both remote from the heat source heating element and also uninfluenced by any adhesive residues which can issue from the discharge end of the cartridge. The advantageous handling properties are therefore further enhanced by virtue of that measure.
It has also proven to be particularly preferable for the projections providing the rotation-preventing means to be arranged in a star configuration and in accordance with a further preferred feature to be formed in one piece out of a (metal) material providing the spout so that, with the best possible securing action to prevent rotational movement, the projections are still easy to shape and the associated tooling costs for manufacturing installations remain low.
Aluminum has proven to be a particularly advantageous material for heat transfer as it is particularly heat-conductive so that in accordance with a further preferred embodiment of the invention the adhesive cartridge is made from aluminum, in which case in accordance with a further preferred feature the spout portion is also formed integrally on the cylindrical cartridge body.
For the purposes of reliable (re-)closure of the discharge opening after use, it has proven desirable to provide a suitable closure cap for the adhesive cartridge, which cap in accordance with a development of the invention is fixed by a screw action on to a screwthread provided on the spout portion. To provide protection from contamination and fouling (for example due to the issue of adhesive) it has proven advantageous in that respect for that male screwthread to be provided in the spout portion as closely as possible to the cylindrical cartridge body.
In accordance with a second embodiment of the invention the valve means provided in accordance with the invention provide that, due to the predetermined counteracting pressure, any adhesive that issues first has to overcome a corresponding force before a discharge flow can take place. That occurs however only when the piston element is intentionally subjected to the action of a force, but not if (in the rest condition) the piston element is not actuated. That advantageously and effectively provides that an unnecessary (unintentional) discharge flow of adhesive out of the discharge end is prevented as soon as an operator ceases to actuate the piston element.
In that respect it has proven to be particularly preferred (best mode) for the valve means to be in the form of a ball pressure valve and as a further preferred feature for a closure ball of the ball pressure valve to be caused to act against the force of a spring, in particular a coil spring. The counteracting pressure or the closing force can then be adjusted by virtue of a suitable selection of the spring.
There is also the further advantage that the meterability action of the device is also facilitated from the point of view of a user in practical use of the device by virtue of the counteracting pressure which is predetermined or which can be predetermined by virtue of the choice of spring, insofar as practical application of the adhesive to a work location is also markedly facilitated thereby.
It is further preferred for the ball pressure valve to be of a modular nature, that is to say the members involved in the valve operation, in particular the spring and the ball, are provided in an associated housing and that housing is then to be provided in the form of a module in the spout portion of the adhesive cartridge so that simplified fitment of the module is possible.
With those measures the invention therefore makes it possible further to improve the properties of use, which in any case are already comfortable, of cartridge-based hot-melt adhesive applicator devices, insofar as more specifically the improved adhesive cartridges afforded in accordance with the present invention combine advantageous technical properties in operation, for example in terms of heat transfer, with simplicity of manufacture which is suitable for large-scale series production, while also affording protection from the accidental discharge of adhesive, and additionally improving the metering properties and thus facilitating in particular also professional use.